Steering column for a motor vehicle

ABSTRACT

A steering column for a motor vehicle may include a steering shaft mounted in a casing unit so as to be rotatable about a longitudinal axis, and a feedback actuator that has an electric motor with a motor shaft that is aligned axially along a motor axis, arranged at a distance parallel to the longitudinal axis, and coupled to the steering shaft via a transmission. The motor is connected to a control unit for electrical operation. The control unit may be integrated with the feedback actuator. And the transmission may be arranged axially between the motor and the control unit.

CROSS REFERENCE TO RELATED APPLICATION

This application is a U.S. Non-Provisional that claims priority toGerman Patent Application No. DE 10 2022 200 667.4, filed Jan. 21, 2022,the entire contents of which are incorporated herein by reference.

FIELD

The present disclosure generally relates to steering columns, includingsteering columns for motor vehicles that include feedback actuators.

BACKGROUND

Steer-by-wire steering systems for motor vehicles, like conventionalmechanical steering systems, accept manual steering commands from thedriver by the turning of a steering wheel of an input unit that isattached to the driver's end of a steering shaft, at the rear in thedirection of travel. However, the steering shaft is not mechanicallyconnected via a steering gear to the wheels to be steered, but acts incombination with angle-of-rotation, or torque, sensors that sense theinput steering command and transmit an electrical control signaldetermined therefrom to a steering adjuster that sets a correspondingsteering angle of the wheels by means of an electric positioning drive.

In the case of steer-by-wire steering systems, the driver receives nodirect mechanical feedback from the steered wheels via the steeringtrain, which in the case of conventional mechanically coupled steeringsystems is fed back to the steering wheel, via the steering gear and themechanically continuous steering shaft, as a reaction moment, orrestoring moment, in dependence on the road surface, the vehicle speed,the current steering angle and other operating conditions. The lack ofhaptic feedback makes it difficult for the driver to reliably sensecurrent driving situations and perform appropriate steering manoeuvres,which impairs the steerability of the vehicle, and thus driving safety.

In order to create a realistic driving experience, it is known in theprior art to sense parameters such as vehicle speed, steering angle,steering reaction moment and the like from an actual real-time drivingsituation, or to calculate them in a simulation, and from these to forma feedback signal that is fed into a feedback actuator. The feedbackactuator has an electric control unit and, connected to it, an electricmotor, the motor shaft of which is coupled to the steering shaft via atransmission. During driving, the motor is electrically operated by thecontrol unit in order to couple a restoring moment (feedback moment),corresponding to the real reaction moment, into the steering wheel viathe steering shaft. Such “force-feedback” systems give the driver theimpression of a real driving situation as with conventional steering,which facilitates an intuitive reaction.

A generic steering column of the type mentioned above is known from DE603 03 081 T2. The motor of the feedback actuator is attached to thecasing unit laterally with respect to the longitudinal axis. The motorshaft is coupled to the steering shaft via a transmission. The controlunit is realized separately, and may be attached to the steering column.The disadvantage of this design is the large amount of installationspace required and the difficulty in mounting.

It has also been proposed, in a non-generic configuration, to integratethe motor of the feedback actuator, with its motor shaft coaxial withthe longitudinal axis, within the casing unit. However, this limits theinstallation space of the feedback actuator due to the casing unit, andboth the constructional adaptation and the production and mounting aremore complex than in the generic design.

Thus a need exists for a more compact design and easier production andmounting.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a schematic view of an example steer-by-wire-steering system.

FIG. 2 is a schematic, perspective view of an example feedback actuator.

FIG. 3 is a schematic, perspective view of part of the feedback actuatoraccording to FIG. 2 .

FIG. 4 is a perspective view of the feedback actuator as in FIG. 3 .

FIG. 5 is a schematic, perspective view of the feedback actuatoraccording to FIGS. 2 to 4 with an actuator housing.

FIG. 6 is a side view transverse to a longitudinal axis of the feedbackactuator according to FIG. 5 .

DETAILED DESCRIPTION

Although certain example methods and apparatus have been describedherein, the scope of coverage of this patent is not limited thereto. Onthe contrary, this patent covers all methods, apparatus, and articles ofmanufacture fairly falling within the scope of the appended claimseither literally or under the doctrine of equivalents. Moreover, thosehaving ordinary skill in the art will understand that reciting “a”element or “an” element in the appended claims does not restrict thoseclaims to articles, apparatuses, systems, methods, or the like havingonly one of that element, even where other elements in the same claim ordifferent claims are preceded by “at least one” or similar language.Similarly, it should be understood that the steps of any method claimsneed not necessarily be performed in the order in which they arerecited, unless so required by the context of the claims. In addition,all references to one skilled in the art shall be understood to refer toone having ordinary skill in the art.

The present disclosure generally relates to steering columns for motorvehicles. In one example, a steering column may comprise a steeringshaft mounted in a casing unit so as to be rotatable about alongitudinal axis, and a feedback actuator, which has an electric motorcomprising a motor shaft that is aligned axially along a motor axis,arranged at a distance parallel to the longitudinal axis and coupled tothe steering shaft via a transmission, the motor being connected to acontrol unit for the purpose of electrical operation. The control unitmay be integrated with the feedback actuator, the transmission beingarranged axially between the motor and the control unit.

It should be understood that the directional indications used herein toidentify the position and arrangement of the individual functionalelements relate throughout to the installation position of the steeringcolumn in the direction of travel of the vehicle, with the front orlower end on the body side facing forwards in the direction of traveland, correspondingly, the rear or upper end facing rearwards contrary tothe direction of travel, towards the driver's position in the vehicleinterior.

A manual steering handle, for example a steering wheel, can be attachedto the rear axial end of the steering shaft.

The motor axis is arranged parallel to the longitudinal axis, in whichcase a solid angle of the axes relative to each other of up to 10° mayalso be understood as parallel in the sense of the invention. Accordingto the invention, the electric control unit, which has electricalcomponents for operating the motor, is realized, together with the motorand the transmission, as an integrated unit. The transmission in thiscase is attached in front of the motor, as viewed from the motor, andthe control unit is attached in front of the transmission, i.e. in thefront region of the feedback actuator that is remote from the motor.This feedback actuator unit can be compactly designed as an entity, andcan be mounted with little difficulty on the outside of the casing unitduring production, such that only an electrical connection of thefeedback actuator to the vehicle electrical system is required. It isthus possible to achieve a reduced effort in production and mounting,and the installation space requirement can be kept small due to theintegrated design.

Another advantage is that the structural size and configuration of thefeedback actuator is not limited by the dimensions of the casing unit,thereby allowing greater constructional freedom.

Moreover, it is possible with relatively little effort to use differentconfigurations of feedback actuators that are adapted in respect oftheir performance or other characteristics. This simplifies theconstruction and makes the production of different types of steeringcolumns more flexible than, for example, in the case of the feedbackactuator being arranged inside the casing unit.

It may be provided that the control unit is arranged, on a front side,in front of a front end of the motor shaft. Preferably, the control unitmay also be arranged in front of a front end of the steering shaft. Thetransmission in this case is preferably integrated between a front endportion of the motor shaft and a front end portion of the steeringshaft. It may be realized as a belt drive, having a belt wheel coupledto the motor shaft, and a belt wheel attached in a rotationally fixedmanner to the steering shaft, and a revolving drive belt, which may berealized as a toothed belt, V-belt or flat belt. Such a belt drive issmooth-running and light. Alternatively or additionally, thetransmission may comprise gearwheels. According to the invention, thecontrol unit is positioned in front of the front-side axial end faces ofthe transmission shafts. It is possible in this case for the controlunit not to project over the transmission. This arrangement has theadvantage that a compact design is possible.

An advantageous embodiment is that the feedback actuator has an actuatorhousing attached to the outside of the casing unit. The transmission andthe control unit are preferably housed in the actuator housing. Themotor arranged outside the casing unit may be attached to the actuatorhousing, or may also be integrated in the actuator housing. The controlunit, including the electrical connection to the motor, may be housed inthe actuator housing, protected against external mechanical andelectrical influences. A robust and compact embodiment can thus beachieved.

It may preferably be provided that the control unit is arranged axiallyin the actuator housing with respect to the motor shaft. According tothe invention, the transmission is arranged in front of the motor,axially between the motor and the control unit with respect to the motorshaft, and the control unit is arranged on the front side of thetransmission that is remote from the motor. This allows the control unitto be arranged in a structurally simple and protected manner, separatefrom the mechanically moving parts of the motor and transmission.

It may be advantageous for the actuator housing to have a controlhousing. The control housing may preferably be attached to the actuatorhousing at the front, on the front side that faces away from thetransmission, and may thus form a front-side front closure of theactuator housing. The control unit may be housed in the control housing.The control housing may be realized, for example, in the form of a hoodor cap, and may be attachable to the actuator housing in such a mannerthat it can at least partially encompass the control unit, or preferablycompletely enclose it together with walls of the actuator housing. Acover may also be provided, which covers towards the front a housinginterior of the actuator housing or control housing that houses thecontrol unit. According to the invention, the control unit in this caseis arranged axially between the control housing and the transmission.The connection between the actuator housing and the control housing ispreferably sealed, such that an arrangement that is well protectedagainst moisture, dust and other potential external harmful influencescan be realized. The seal may be realized as cord seal, or as anelastomer seal moulded onto one of the housing components.

The control housing may preferably be detachably connected to theactuator housing, for example by means of detachable connection elementssuch as screws or the like. This provides for simplicity of productionand mounting. In an advantageous further development, it may be providedthat the screws are realized as breakaway screws or as screws that havea non-standard drive, such that demounting by non-expert persons isavoided or at least made more difficult.

It is possible for the actuator housing to have a transmission housing.The transmission housing may be attached axially at the rear of theactuator housing. Thus, it is arranged on the rear side that faces awayfrom the control unit and faces towards the motor. Gearwheels of thetransmission may be mounted in the transmission housing. The motor maybe attached, for example flange-mounted, to the control housing. Thetransmission housing may be realized separately and connected to theactuator housing, or at least partially integrated with the actuatorhousing. It is thus possible to realize a space-saving embodiment thatis easily mounted and produced.

The transmission housing may be positioned axially between a controlhousing and the motor. This arrangement has the advantage that thecontrol unit and the transmission are each easily accessibleindependently of each other and are protected against externalinfluences.

The transmission housing may preferably be detachably connected to theactuator housing, for example by means of detachable connection elementssuch as screws or the like. This provides for simplicity of productionand mounting. The connection may preferably be sealed, such that thetransmission is protected against external harmful influences such asmoisture, dust and the like.

It is advantageous for the actuator housing to have connection elementsthat can be connected to the casing unit. This enables the feedbackactuator to be fastened to the steering column, which may havecorresponding connection elements, in a simple, easily mountable manner.

An advantageous embodiment may provide that the control unit has aprinted circuit board having a planar extent. The printed circuit boardconstitutes a printed board on which electrical components of thecontrol unit are mechanically fastened and electrically interconnectedvia conducting tracks. The printed circuit board may preferably bearranged with its planar extent transverse (normal) to the motor axisand longitudinal axis. According to the invention, the printed circuitboard may preferably be arranged, on a front side, in front of the motorshaft and the steering shaft. An advantage is that the printed circuitboard can be easily adapted, in respect of its shape and dimensions, inorder for it to be housed, for example, in a control housing. Theelectrical connectors required for terminating to the motor and thevehicle electrical system may also be attached to the printed circuitboard, such that a modular, easily mounted control unit can be provided.

It is advantageous for the control unit to be connected to the motor viacontrol lines extending in the axial direction through the transmission.The control lines bridge the transmission in the axial direction, whichis positioned between the control unit arranged at the front and themotor attached at the rear. One advantage of this is that the controllines can be housed in the actuator housing, protected against harmfulmechanical and electrical influences.

It may preferably be provided that connection lines of the control unitthat can be connected to the control unit are routed out of the feedbackactuator towards the front. The connection lines serve to electricallyconnect the feedback actuator to the vehicle electrical system, andinclude electric power supply leads and control lines. For example, theconnection lines may be routed out of the actuator housing through afrontally attached, front-side cover or a control housing to theoutside. There they may be connected, for example via a plug-and-socketconnection, to an on-board electronics system of the motor vehicle. Anadvantage of this arrangement is that the connection can be effectedentirely in a front region where the steering column is held on thevehicle body, and electrical connection cables can be routed easily andout of the passenger compartment of the vehicle.

It may be advantageous for the control unit to have at least one sensorelement interacting with the steering shaft and/or the motor shaft. Thesensor element may comprise, for example, an electronic rotary sensorfor sensing a rotation or angular position of the steering shaft and/orthe motor shaft. This enables measurement of the rotational movementsgenerated by the feedback actuator, and electronic closed-loop controlof the feedback torque generated may be effected. In addition, bycomparison of the rotations of the steering shaft and motor shaft,functioning can be monitored, for example as to whether there isslippage occurring in the transmission or the torque transmission isbeing otherwise disrupted. The functional and operational safety canthus be increased. The arrangement according to the invention enablesthe sensor element or elements to be positioned in the front region ofthe steering shaft and/or motor shaft in a functionally reliable andeasily mountable manner.

One or more sensor elements may be arranged, for example, on a printedcircuit board of the control unit. This provides for simplicity ofproduction and a compact design.

The directional indications relate to the regular direction of travel ofa vehicle, which is not represented in detail, the direction to thefront being indicated in the figures by an arrow as direction V, andcorrespondingly the opposite direction H to the rear.

Shown schematically in FIG. 1 is a steer-by-wire steering system 1comprising, as an input unit, a steering column 2 that is connected toan electric steering drive 4 via an electric lead 3.

The steering drive 4 comprises a positioning motor 41, which isconnected to the electric connection line 3 and which introduces asteering positioning moment into a steering gear 42. There, the steeringpositioning moment is converted, via a pinion 43 and a toothed rack 44,into a translational movement of track rods 45, as a result of which asteering angle of the steered wheels 46 is effected, in a manner knownper se, by pivoting of steering knuckles. Alternatively, the steeredwheels 46 may be connected to individually operable electric positioningdrives in order to realise individual wheel steering.

The input unit 2 has a steering shaft 51, to the rear end of which asteering wheel 52 is attached, and which is mounted in a casing unit 53so as to be rotatable about a longitudinal axis L directed from the rearto the front.

The steering column 2 has a feedback actuator 6, which is represented indifferent views on the casing unit 53 in FIGS. 2, 3, 4, 5 and 6 . FIG. 2shows an exposed general view of the feedback actuator 6, which isattached to the casing unit 31 (indicated by a dashed line).

The feedback actuator 6 has an actuator housing 61, attached to thefront side of which there is a hood-shaped control housing 62.

Attached to the rear of the actuator housing 61 there is a transmissionhousing 63.

The housings 61, 62 and 63 may be flange-connected to one another, forexample by means of connecting bolts, the dividing plane between thehousings 61 and 62, or 61 and 63, in each case being transverse to thelongitudinal axis L.

An electric motor 7 is attached to the actuator housing 61 from therear, for example flange-connected to the transmission housing 63 as inthe example shown.

The motor 7 has a motor shaft 71 that extends along a motor axis M, ascan be seen in FIGS. 6 and 3 , in which the control housing 62 and thegear housing 63 are omitted for clarity. In contrast to FIGS. 3 and 4 ,inn FIGS. 5 and 6 the entire actuator housing 61 is additionally omittedso that the arrangement of the rest of the functional parts can be seen.

The longitudinal axis L and the motor axis M are parallel to each otherand are spaced apart by a distance A. This distance A may preferably beat least as great as half the diameter, i.e. the radius of the casingunit 53.

Arranged in the transmission housing 63 there is a transmission 8, whichin the example shown is realized as a belt transmission or toothed-belttransmission. This comprises a drive-side belt wheel 81 fixed on themotor shaft, a driven-side belt wheel 82 fixed on the steering shaft 51,and a belt 83 revolving around the belt wheels 81 and 82.

Arranged in the control housing 62 there is a control unit 9. Thiscomprises a printed circuit board 91, having a planar extent transverseto the axes L and M, on which a plurality of electronic components arearranged and electrically connected to each other via conducting tracks.

It can be clearly seen from FIG. 6 that the circuit board is arranged,at the front, in front of the transmission 8. In other words, thetransmission 8 is arranged, axially in relation to the longitudinal axisL or the motor axis M, between the control unit 9 and the motor 7.

The shape and dimensions of the printed circuit board 91 are adapted insuch a manner to the interior of the control housing 62 that, when inthe assembled state as in FIG. 2 , it is fully received in the actuatorhousing 61 and sealed with respect to the exterior. Preferably in thiscase, the interior of the control housing 82 is also separated from andsealed with respect to the transmission housing 63.

An electronic rotary sensor 92 may preferably be arranged on the frontaxial front side of the motor shaft 71 and of the circuit board 91, forexample comprising a Hall sensor, an optical incremental encoder or thelike. This can be used to sense a rotational movement and/or an angularposition of the motor shaft 71.

Similarly, an electronic rotary sensor 92 may preferably be arranged onthe front axial end of the steering shaft 51 and of the circuit board91, likewise comprising, for example, a Hall sensor, an opticalincremental encoder or the like. This can be used to sense a rotationalmovement and/or an angular position of the motor shaft 71.

Control lines 94, which serve to operate the motor 7 through the controlunit 9 and bridge the transmission 8 in the axial direction, may bearranged between the circuit board 91 and the motor 7. The control lines94 may be arranged in a protected manner inside the actuator housing 61,as represented in FIG. 4 , for example.

The circuit board 91 may be connected to an electrical connector 95 thathas connection lines electrically connected to the circuit board and,for example, a socket attached to the outside of the control housing 62.A corresponding connector on a lead of the vehicle electrical system maybe easily connected to the connector 95 in order to electrically couplethe control unit 9 to the vehicle.

A particular advantage of the arrangement according to the invention isthat, for the purpose of mounting, with the transmission 8 alreadymounted the circuit board 91 of the control unit 9 can simply beinserted axially from the front into the actuator housing 61 and fixedto a holding element 64 (see FIG. 6 ), for example by screw fastening,riveting or the like. In this way, the rotary sensors 92 and 93 can beassembled ready for operation without additional adjustment and withoutthe need for additional connecting leads as in the prior art.

The control unit 9 is housed in a protected manner in the subsequentlyattached and fixed control housing 62.

LIST OF REFERENCES

1 steering system

2 input unit

21 longitudinal axis

3 lead

4 steering drive

41 positioning motor

42 steering gear

43 pinion

44 toothed rack

45 track rod

46 wheel

5 feedback actuator

51 steering shaft

52 steering wheel

53 casing unit

6 feedback actuator

61 actuator housing

62 control housing

63 transmission housing

64 holding element

7 motor

71 motor shaft

8 transmission

81, 82 belt wheel

83 belt

9 control unit

91 printed circuit board

92, 93 rotary sensor

94 control line

95 connector (connection lines)

L longitudinal axis

M motor axis

A distance

V direction forwards

H direction rearwards

What is claimed is:
 1. A steering column for a motor vehicle,comprising: a steering shaft mounted in a casing unit so as to berotatable about a longitudinal axis; a feedback actuator that has anelectric motor comprising a motor shaft that is aligned axially along amotor axis, arranged at a distance parallel to the longitudinal axis,and coupled to the steering shaft via a transmission; and a controlunit, wherein the motor is connected to the control unit for electricaloperation, wherein the control unit is integrated with the feedbackactuator, wherein the transmission is disposed axially between the motorand the control unit.
 2. The steering column of claim 1 wherein thecontrol unit is arranged, on a front side, in front of a front end ofthe motor shaft.
 3. The steering column of claim 1 wherein the feedbackactuator has an actuator housing that is attached to an outside of thecasing unit.
 4. The steering column of claim 3 wherein the control unitis arranged axially in the actuator housing with respect to the motorshaft.
 5. The steering column of claim 3 wherein the actuator housinghas a control housing.
 6. The steering column of claim 3 wherein theactuator housing has a transmission housing.
 7. The steering column ofclaim 3 wherein the actuator housing has connection elements that aresized and shaped for connection to the casing unit.
 8. The steeringcolumn of claim 1 wherein the control unit includes a printed circuitboard that has a planar extent.
 9. The steering column of claim 1wherein the control unit is connected to the motor via control linesextending in an axial direction through the transmission.
 10. Thesteering column of claim 1 wherein connection lines of the control unitthat are sized and shaped for connection to the control unit are routedout of the feedback actuator towards a front.
 11. The steering column ofclaim 1 wherein the control unit has a sensor element that interactswith the steering shaft and/or the motor shaft.